"these fruit are" is quite rare in comparison, actually: http://bit.ly/2JAIBc5
That an uncountable noun has a plural meaning "different types of [uncountable noun]" is a standard phenomenon. Sometimes such usage is so common, it can be easy to miss the fact that the noun is uncountable: two juices, two soups (of course these have the separate interpretation "two portions of soup/juice").
It would be nice if someone would verify whether फल can also be used in an uncountable manner. If not, then the unambiguous interpretation of this sentence would be "These pieces of fruit are cold."
To determine if the plural of any word is ok or not, see if it fits with the phrase "all of the X" or "both of the X".
If you were to ask a grocer if the two apples on display are cold cold, he could respond "both of the fruits are cold". You could then ask if this applied to the rest of the apples and he could respond "all of the fruit is cold". You could then ask if this includes the apples, bananas, and mangoes and he could respond "all of my fruits are cold".
So the singular form "fruit" can refer to any quantity, and the plural form "fruits" can refer to multiple types of fruit as well as multiple fruit items.
You can do this semi-collective/semi-countable thing with the word "fruit" in a way that you couldn't with a word like "vegetable". "All of the vegetable are cold" sounds very wrong.
I've gotten quite a number of accepted report e-mails (not sure what kind of acknowledgement you might have been expecting apart from this).
They have posted two related threads in the past week:
In the Norwegian course, the response in the discussion is prompt. The issue about fruit or fruits has had no response from the course contributors. That is my beef.
I studied Hindi in school from the age of 10 (not very well) and I do remember that Hindi grammar does have a few nasty twists and turns (e.g. the oblique case). It would help if there was some helpful explanations at the bottom of each exercise as with the Norwegian course, but that is a separate beef.
It's not for no reason the Norwegian course is commonly viewed as such a standout. The Hindi contributors already having reviewed 60% of the tree if the brief time it's been in beta constitutes an exceptional clip. Granted, the tree is short, but it makes sense they've focused efforts there, and they've been more transparent about their efforts on that front than I've ever seen, and I've started quite a few courses in beta.
It would help if there was some helpful explanations at the bottom of each exercise as with the Norwegian course
Do you mean when your answer is counted wrong?
for this sentence, you can see that it's (grammatically) singular by the demonstrative ये as opposed to यह, and the verb हैं as opposed to है. See the comments about how for English speakers, "these fruits" and "this fruit" are pretty much synonymous, but that's how the grammatical number is showing up in the Hindi here.